The present invention generally relates to a technology for recovering data.
Generally, information systems are capable of recovering lost data when data is lost as a result of a storage system fault, data corruption caused by a computer virus, an erroneous operation by the user, or the like, by acquiring backups at regular intervals.
One emerging backup and recovery technology is a backup and recovery technology that uses journaling (See published U.S. Patent Application No. 2005/0015416, for example). Published U.S. Patent Application No. 2005/0015416 discloses a technology that acquires a snapshot (logical image of a full backup or partial backup or the like taken at a specified time point of a logical group constituted by one or more data volumes (called a ‘journal group’ hereinbelow), stores subsequent write data to the data volumes in journal volumes associated with the journal group as journals (called an ‘after journal’), and applies a series of after journals according to the order in which same were written to the acquired snapshot, whereby data at a specified time point are recovered. This is an example of a technology generally known as ‘Continuous Data Protection’ or, in its abbreviated form, ‘CDP’.
Furthermore, Published U.S. Patent Application No. 2005/0015416 also proposes a method that cancels the after journal application when data that has been recovered by the after journal application is found to have been corrupted. Published U.S. Patent Application No. 2005/0015416 discloses the fact that localized data that is overwritten by the after journal application is saved to the journal volume and, when the after journal application is cancelled, the data is recovered to the snapshot prior to the after journal application in a short time by applying the saved data to the original point (writing the save data) to the snapshot to which the after journal is applied. The saved data is known as the ‘before journal’.
In Japanese Patent Application Laid Open No. 2004-252686, a technology that simultaneously acquires an after journal and before journal during writing from the host computer is also disclosed. According to this technology, previous data can be recovered by applying the before journal to the operating data volume. Further, the after journal, before journal and the journal management metadata are collected and simply called ‘journals’. Further, the snapshot which is the journal application target during recovery is called the ‘base snapshot’.
Generally, in the recovery of a computer system, it is necessary to reduce the time required for completing the recovery process (recovery time) as much as possible.
In addition, in the recovery of a computer system, sometimes time point data of either of two or more times may be recovered. For example, when a file that has been deleted by an erroneous user operation is restored, any time point data may be restored from the file creation time point up until immediately before the file was deleted. Further, in the case that the point of the time the data must be recovered existed at is uncertain (for example, the period the data must be recovered existed is not known), we must recover the data which existed at the point of time specified from rough estimate, and validate the recovered data. So too in this case, this does not necessarily mean that data at a strictly determined time point is recovered but, rather, that data of any time point in a certain time range (close to 10:00, for example) is recovered. Further, any time point data between batch processes may also be recovered when data updated only by the contents batch processing among all the data of the database (DB) is recovered. That is, any time point data between the events of applications and tasks may be recovered. In addition, even when a system that has been halted as a result of a data fault or the like is restarted, any time point data up to and including the data fault may be restored. However, this is limited to cases where the latest data is not needed for the restart. For example, in the case of the mail server, because the latest mail data is not required for the restart, this applies to this example (there may be a need to restore the latest mail data).
It should be noted that in the case of the technology disclosed in Published U.S. Patent Application No. 2005/0015416 and Japanese Patent Application Laid Open No. 2004-252686, the time interval (recovery time) required to recover data of the specified time point (recovery point) depends on the number and size of the journals applied to the base snapshot during recovery. That is, the recovery times of the data at each time point are different from one another. However, in Published U.S. Patent Application No. 2005/0015416 and Japanese Patent Application Laid Open No. 2004-252686, when the user chooses which time point data to recover, the information relating to the recovery time is not displayed. Hence, when the time point data of any of two or more time points may be recovered, there is the problem that data that requires a longer recovery time than necessary is sometimes recovered.